JP3397142B2 - How to measure anchor tension - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring anchor tension, and more particularly to a method for measuring anchor tension by a relatively simple method.

[0002]

2. Description of the Related Art A ground anchor construction method is known, in which an anchor is embedded in an object to be stabilized, such as the ground, as a measure for stabilizing the ground and slopes and structures such as retaining walls that are prone to landslides. .

An anchor embedded by this ground anchor method is provided with a head portion, a tension portion and a fixing portion, and a tension tendon is arranged inside. The tendon is covered with a sheath tube in the pulling section, and is fixed by grout in the ground in the fixing section.

When introducing tension into the tendon, a tensioning tool such as a jack is attached to the head, and the tension is introduced by pulling the tendon. The tendon is installed by installing a fixing tool on the head. , This tension is maintained.

The tension reaction force due to the tension at this time is transmitted to the ground side directly or via the pressure bearing plate, and such tension reaction force is constantly applied to the ground to stabilize the ground.

In this case, the tension applied to the tendon is
It is an extremely important management item to ensure the stability of the ground, etc. When introducing tension, the size is measured with a measuring device such as a load cell or an axial force meter.

However, after the anchor work is completed, for example,
Several decades later, when trying to measure tension, such as when performing maintenance, there was a technical problem explained below.

[0008]

That is, since the above-mentioned measuring device is expensive, it is very difficult in terms of cost to install it on all anchors and measure the change in tension over time. Therefore, when removing the fixing tool and re-tensioning, a lift-off test is also performed to measure the tension with the above-mentioned measuring device. Has a problem that it is very difficult to measure at an angle close to vertical.

The present invention has been made in view of the above conventional problems, and an object of the present invention is to measure changes in anchor tension with time by a relatively simple method. It is to provide a method that can.

In order to achieve the above object, the present invention provides a fixing tool in which an anchor is embedded in an object to be tightened, such as the ground or a structure, and fixed to a protruding end of a tension tendon disposed in the anchor. In the anchor construction method, which introduces a tension force into the tendon, and transmits a tension reaction force associated with the tension force to the tightening object directly or through a pressure plate, between the fixing tool and the pressure plate, or Between the fixing tool and the tightening target, an elastic member for urging the fixing member and the tightening object is interposed, and a measuring gauge for detecting displacement in the thickness direction of the elastic member is provided. Measurement of the tension of the tendon from the value of anchor tension
The measuring gauge may be the fixing device or the support.
Measuring rod whose one end is fixed to the pressure plate and the tightening target
One end is fixed to the object side and extends parallel to the measuring rod.
And a reference rod for the reference rod,
The relative movement amount of the measuring rod is measured in the thickness direction of the elastic member.
It was detected as the displacement of. According to the anchor tension measuring method configured as described above, when the tension of the installed anchor is loosened due to a change with time, between the fixing tool and the pressure plate, or between the fixing tool and the tightening target. Since the elastic member for urging the both members in the direction of separating them is interposed between them, the elastic member extends in response to this loosening and assists the tension force. When the elastic member extends, its length in the thickness direction changes, and displacement occurs. In this case, according to the present invention, the total
The measuring gauge is the one whose one end is fixed to the fixing tool or pressure plate.
Fixed rod and one end fixed to the object to be tightened,
And a reference rod extending parallel to the
The amount of relative movement of the measuring rod to the thickness of the elastic member
It is detected as a displacement in the normal direction. Therefore , even when the tightening target side is displaced, the displacement of the elastic member can be obtained from the relative movement amount of the measurement rod with respect to the reference rod. The measurement rod and the reference rod may be installed so as to protrude to the outside of the head cap that covers the outer periphery of the fixing device. According to this configuration, the current tension force of the tendon can be measured from the value of the measurement gauge without removing the head cap of the fixing tool. The elastic member may be formed of a disc spring having a through hole formed in the center through which the tendon is inserted. According to this configuration, the disc spring has a region in which the load displacement is small even if the deformation progresses in the relationship between the load and the displacement, and by utilizing this region, the tension force of the tendon is changed over time. It can help to reduce such changes. Further, in the above-mentioned region, even if the tension force of the tendon is slightly reduced, the displacement of the disc spring in the thickness direction becomes large, so that the measurement with the measuring gauge can be easily and easily performed.

[0011]

Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. Figure 1
3 to 3 show an embodiment of a method for measuring anchor tension according to the present invention.

The tension measuring method shown in the figure illustrates the case where the present invention is applied to the ground anchor construction method. FIG. 1 is a cross-sectional view showing a state in which a permanent anchor 12 is embedded in a slope ground 10.

The anchor 12 is fixedly installed at a deep portion by pouring a grout material 16 into a drilled hole 14 drilled in the ground 10, and a tension tendon 18 is arranged in the anchor 12. It is set up.

The tendon 18 has a form in which a steel wire and a steel material are covered with a sheath, and a plurality of tendons 18 are used in this embodiment. A fixing unit 20 is provided on the head side where the anchor 12 projects outward from the slope ground 10.

The fixing portion 20 of this embodiment has a concrete sloped surface 2 formed on the surface side of the slope ground 10 and is disposed in a recess 24 provided in the sloped surface 22.
The fixing unit 20 includes a base plate 26, a disc spring 28 (elastic member), a pressure support plate 30, a fixing tool 32, and a head cap 34.

The pedestal plate 26 is fixed to the bottom surface of the recess 24 and has a through hole for inserting the tendon 18 formed in the center thereof. The pedestal plate 26 has a double cylindrical structure having an end open on the outer peripheral side of the through hole. Inner and outer guide pipes 38 and 36 are vertically provided.

The upper and lower ends of the inner guide pipe 38 are open,
The tendon 18 is vertically inserted along the longitudinal direction of the inserted tendon 18, and the upper end side thereof is fixed to the lower surface side of the pressure bearing plate 30.

As shown in detail in FIG. 2, the disc spring 28 has a substantially frustoconical appearance, and has small-diameter and large-diameter through holes 28a, 28b formed at the upper and lower ends. The small-diameter through hole 28a is sized so that the inner guide pipe 38 can be inserted therethrough.

FIG. 3 shows the relationship between the load and displacement of the disc spring 28 used in this embodiment. The relationship between the load and the displacement shown in the figure is as shown in FIG. 2, when the large-diameter through-hole 28b is placed on a flat surface and the load p is applied from the small-diameter through-hole 28a side. The displacement amount u is measured.

In the relation between the applied load and the displacement shown in FIG. 3, the disc spring 28 has a region in which the load displacement is small even if the deformation progresses in the substantially central portion thereof. In such a region and a region located in the preceding stage where the load and the displacement are in a substantially proportional relationship, the material and thickness of the disc spring 28, the disc spring 2
8 in series or in parallel and through holes 28a, 28
It depends on the size of b.

In the case of this embodiment, as shown in FIG.
A total of six disc springs 28 are used in a stacked state, and the disc springs 28 that are vertically adjacent to each other are arranged such that the small-diameter through holes 28a and the large-diameter through holes 28b are in contact with each other. .

The stacked disc springs 28 are installed so that the peripheral edge of the small-diameter through hole 28a in the lowermost stage abuts on the upper surface of the pedestal plate 26. The pressure bearing plate 30 is installed such that the peripheral edge of the small-diameter through hole 28a of the uppermost disc spring 28 is in contact with the lower surface side with the tendon 18 inserted in the central portion.

A joint plate 40 having a diameter smaller than the pressure bearing plate 30 is placed on the upper surface side of the pressure bearing plate 30, and a fixing tool 32 is installed on the upper surface side of the joint plate 40.
The fixing tool 32 includes a fixing plate 32a and a wedge cone 32b.
It has and.

The head cap 34 is fixed to the outer peripheral edge of the recess 24 so as to cover the outer periphery of the fixing tool 32, and the inside thereof is filled with a rust preventive material 42. A measuring gauge 44 is installed in the fixing unit 20 configured as described above.

The measuring gauge 44 detects the displacement l of the disc spring 28 in the thickness direction, and the measuring gauge 44 of this embodiment is substantially the base plate 2 to be tightened.
6 has a reference rod 44a whose one end side is fixed to the upper surface of 6, and a measurement rod 44b whose one end is fixed to the upper surface of the pressure bearing plate 30.

The reference and measurement rods 44a and 44b are
They are provided at relatively close intervals to each other, extend parallel to the head cap 34 side, penetrate the head cap 34, and project to the outside.

Although not shown in the drawings, a sealing material for preventing the rust preventive material 42 from flowing out is interposed at a portion where the rods 44a and 44b penetrate the head cap 34.

In the measuring gauge 44 thus constructed, when the thickness of the disc spring 28 changes, the measuring rod 44
b moves in response to this displacement, the distance between the tip of the reference rod 44a and the tip of the measuring rod 44b differs, and the displacement l in the thickness direction of the disc spring 28 is observed by visually observing this amount of movement. I understand.

When the tension force is introduced into the tendon 18 of the anchor 12, the tendon 1 is attached before the fixing tool 32 is mounted.
Attach a tension device such as a jack to the end of 8
Tension is introduced by pulling 8.

Then, in this state, the fixing plate 32a is placed on the upper surface side of the joint plate 40, the wedge cones 32b are attached to the respective tendons 18, and the wedge cones 32b are inserted into the tapered holes of the fixing plate 32a. , Remove the tension of the tensioning device.

When the tensile force is removed, the tension reaction force introduced into the tendon 18 is applied to the pressure plate 3 via the fixing tool 32.
The pressure bearing plate 30 transmitted to 0 and receiving the tension reaction force transmits the tension reaction force to the base plate 26 while compressing the disc spring 28.

The pedestal plate 26 is substantially the slope 1
It is the same part as 0, and the ground slope 10 is stabilized by receiving this tension reaction force. And head cap 3
When 4 is attached and the rust preventive material 42 is injected into the inside, installation of one ground anchor is completed.

In such a ground anchor installation completion state, the disc spring 28 is compressed and deformed by receiving the tension reaction force from the pressure support plate 30, and therefore, the pressure support plate 30.
And the pedestal plate 26 are urged in the direction of separating them.

When the tension force introduced into the tendon 18 after installation of the ground anchor is reduced due to loosening, in the case of this embodiment, the bearing plate 30 and the base plate 26 are separated from each other. Since the disc spring 28 that is biased in the direction is interposed, in response to this looseness,
By extending the disc spring 28, a reduced tension force is applied to the disc spring 2
It can be assisted by the biasing force of 8.

In this case, the disc spring 28 has a region in which the load displacement is small even if the deformation progresses in the relationship between the load and the displacement, and by utilizing this region, the tension force of the tendon is changed with time. It is possible to assist in reducing the physical displacement.

That is, in FIG. 3, for example, if the initial tension force is set at the displacement point u1 near the lower limit of the region where the load change is small, even if the displacement changes from this displacement point u1 to the displacement point u2. The load, that is, the fluctuation of the tension force introduced into the tendon 18 becomes very small, and the tension force can be continuously applied to the tendon 18 substantially constant.

At this time, when the disc spring 28 extends, its length in the thickness direction changes. This change in length can be confirmed by visual inspection of the measurement gauge 44. In the case of the present embodiment, the measuring gauge 44 includes a measuring rod 44b and a reference rod 44a, and detects the relative movement amount of the measuring rod 44b with respect to the reference rod 44a as a displacement l of the disc spring 28 in the thickness direction. There is.

That is, the change in length between the tips of the reference and measurement rods 44a and 44b shown in FIG. 1 corresponds to the displacement l of the disc spring 28. Therefore, for example, if the length l1 between the reference and the tips of the measuring rods 44a and 44b at the time of introducing the initial tension is recorded and the length after a predetermined time is l2, then | l1-l2 | The displacement u of the spring 28 can be determined.

With respect to the displacement u thus obtained, if the relationship between the displacement of the disc spring 28 and the load shown in FIG.
The magnitude (absolute value) of the tension force of can be measured.

In the measurement of the tension force by such a measuring gauge 44, for example, as shown in FIG. 3, for the disc spring 28, even if the tension force of the tendon 18 is slightly reduced, the thickness of the disc spring 28 is reduced. Since the displacement u in the depth direction becomes large, the measurement by the measuring gauge 44 can be performed accurately and easily.

Further, in the case of this embodiment, the measuring rod 4
4b and the reference rod 44a are installed so as to project to the outside of the head cap 34 that covers the outer circumference of the fixing tool 32. Therefore, without removing the head cap 34, from the visual value of the measurement gauge 44, the current tendon 18 Can measure the tension of.

The layered state of the disc spring 28 shown in FIG. 1 is not limited to the state shown in FIG.
As shown in FIG. 4 (a), the large-diameter through holes 28 b are stacked so that the large-diameter through holes 28 b are in contact with each other, and the small-diameter through holes 28 a are stacked as shown in FIG. 4 (b). As shown in FIG. 7C, two disc springs 28 may be laminated on the inner surface side.

Although the disc spring 28 is illustrated as the elastic member in the above embodiment, the present invention is not limited to this, and may be a coil spring or a leaf spring, for example. Even when 28 is used, it is not always necessary to stack them.

[0044]

As described above in detail in the embodiments,
According to the anchor tension measuring method of the present invention, it is possible to inexpensively measure changes over time in anchor tension by a relatively simple method.

[Brief description of drawings]

FIG. 1 is an explanatory cross-sectional view of an installed state of a ground anchor to which the measuring method of the present invention is applied.

FIG. 2 is a detailed view of the disc spring shown in FIG.

FIG. 3 is a graph showing a relationship between a displacement and a load of the disc spring shown in FIG.

FIG. 4 is an explanatory view of a modified example of a stacked state of disc springs that can be applied to the ground anchor shown in FIG.

[Simple explanation of symbols]

10 slope ground 12 anchors 18,18a Tendon 20, 20a Fixing part 26 Pedestal plate (object to be tightened) 28 Belleville 30 bearing plate 32 Fixing tool 34 head cap 44 Measuring gauge 44a Reference rod 44b Measuring rod

Claims (3)

(57) [Claims] 1. An anchor is embedded in an object to be tightened, such as the ground or a structure, and a tension is introduced into the tendon through a fixing tool fixed to a protruding end of a tension tendon arranged in the anchor. However, in the anchor construction method for transmitting the tension reaction force associated with this tension force to the tightening object directly or through the pressure plate, between the fixing tool and the pressure plate, or between the fixing tool and the tightening object. An elastic member that urges the two in a direction to separate them from each other is provided between them, and a measurement gauge that detects displacement in the thickness direction of the elastic member is provided, and the tension force of the tendon is measured from the value of the measurement gauge. An anchor tension measuring method , wherein one end of the measuring gauge is fixed to the fixing tool or the pressure plate.
Fixed measuring rod and one end fixed to the tightening target side.
Reference rod extending in parallel with the measuring rod
And a relative movement of the measuring rod with respect to the reference rod.
An anchor tension measuring method , wherein the amount is detected as a displacement of the elastic member in the thickness direction . 2. The measuring rod and the reference rod are the fixed rods.
It protrudes to the outside of the head cap that covers the outer circumference of the garment.
The measurement of the anchor tension force according to claim 1, wherein
Method. 3. The elastic member has the tendon at the center.
Characterized by a disc spring with a through hole inserted
The method for measuring anchor tension according to claim 1 or 2.
Law.